New Insights in the Treatment of Waste Water with Graphene: Dual-Site Adsorption by Sodium Dodecylbenzenesulfonate

For the adsorption of sodium dodecylbenzenesulfonate (SDBS) in aqueous solution on reduced graphene oxide (rGO), it is demonstrated that the dual-site mechanism is strongly favored over the conventional single-site one. The dual-site adsorption isotherm is derived, and regression analysis is successfully applied to experimental UV–vis data (1 g L–1 rGO; 298–318 K; 100–900 mg L–1 SDBS; pH: 4–11), considering reparametrization to minimize the correlation between the parameter estimates (dual site: ΔH° = −37.1 ± 1.3 kJ mol–1; ΔS° = 35.5 ± 4.1 J mol–1 K–1; q∞ = 546.9 ± 8.6 mgSDBS grGO–1). A temperature of 298 K is identified as the optimal operating temperature with contact times of ca. 30 h (700 mg L–1 SDBS). An improved regression analysis strategy, carefully selecting only low contact times (maximal 10 h), allowed assessment of the dual-site adsorption and desorption coefficient as (1.2 ± 0.3) × 10–4 L mgSDBS–1 h–1 and (2.8 ± 0.7) × 10–3 h–1. Moreover, by the additional presence of sodium chloride (1.2 × 104 mg L–1), a much lower contact time of ca. 10 h can be selected to ensure an as good as complete SDBS removal, highlighting the potential of the SDBS/rGO system for wastewater treatment.